Heretofore, there has been provided a remote-controlled travelling robot which incorporates four travelling crawlers and which is used for disposal of dangerous substance in a nuclear power facility or on a flat land (refer to, for example, Japanese Patent Publication No. 63-270). As shown in FIG. 18, this robot is arranged such that crawlers 2, independent from each other, are provided at four corners of a robot body 1, that is, they are attached to the robot body 1 through the intermediary of pivot shafts 2a, respectively, so that they can be pivoted independently from each other. Accordingly, while the crawlers are positioned horizontally for normal travel, they can be made to stand upright for smooth movement in a narrow space and they can be inclined for overriding a bump.
However, in the case of outdoor use of the conventional robot on an off-road place or a place around a stricken area in a wide-area disaster, the robot is remote-controlled in its alert posture such that, in a cave-in area, the rear crawlers 2R are downwardly inclined to direct a stereo camera 3 mounted on the robot body 1 downwardly and forwardly, as shown in FIG. 19(a). The robot can be operated with a certain caution in indoor use since there is no obstacle disturbing the field of view of the camera 3, but, in the case of outdoor use around the stricken area, the field of view can be possibly disturbed by obstacles such as weeds so that the robot sometimes continues to advance even though the front crawlers 2F leave the ground as shown in FIG. 19(b). Should it continue to advance, the front crawlers 2F would become unsupported in their entirety so that the gravitational center of the robot body is shifted forwardly. In such a case, although the operator hurriedly instructs the robot to back up (as shown in FIG. 19(c)), the robot can fall into the cave-in depression since the gravitational center of the robot body is shifted towards the cave-in depression (as shown in FIG. 19(d)). Alternatively, as shown in FIG. 19(e), even though it is initially found that the robot body 1 is inclined forwardly, it cannot be readily determined whether this is caused by a concavity or convexity, or a cave-in depression. Accordingly, the advance of the robot is continued with monitoring. Even through an instruction to back up is issued due to the fact that an increase in inclination is found, the robot can slip (as shown in FIG. 19(f)) and then fall into the cave-in depression since the gravitational center of the robot body is shifted towards the front crawlers 2F (as shown in FIG. 19(d)). In particular, a large gripping force cannot be obtained if it travels on a muddy, sandy or weedy place, and accordingly, the robot tends to slip.
Further, in the case of climbing a bump, the robot normally travels until the front crawlers 2F come into contact with the bump as shown in FIG. 20(a). Then, the robot further advances while the front crawlers 2F are pivoted upwardly and elevated (as shown in FIG. 20(b), and thereafter, the front and rear crawlers 2F, 2R are pivoted downwardly in order to raise the robot body 1 (as shown in FIG. 20(c)) so that the robot advances to bring the rear crawlers 2R into as close contact with the surface of the bump as it possibly can (refer to FIG. 20(d)). However, if the rear crawlers 2R are forced to climb the bump in such a condition that the rear crawlers 2R make contact with an inclined surface of the bump (as shown in FIG. 20(e)), then when the rear crawlers 2R are pivoted upwardly and elevated, the gravitational center of the robot body 1 would be shifted rearwardly and the robot may fall off the bump (refer to FIG. 20(f)) since the gravitational center of the robot body is not always stable on the bump.
The conventional travelling robot is likely to have a risk of a downfall as mentioned above in a natural environment in which a cave-in depression or a bump is present as in a stricken area in a wide-area disaster, and accordingly, their actual activities have to be greatly limited. Further, upon occurrence of a downfall accident, a power transmission system, a structural member or the like can be damaged, and accordingly, there is raised a problem of impossible use of the travelling robot.
Such a remote-control of the robot is carried out by the operator who manipulates four knobs laid on the flat board of a control, for respectively controlling the postures of the crawlers. The rotating angles of the respective knobs exhibit the pivoting angles of the four crawlers, respectively.
However, should a robot having a three-dimensional shape be remote-controlled by means of the knobs laid in a planar configuration, the operator should carry out the posture control for every crawler while visualizing its posture in motion. In particular, such an imaginal control cannot at once cope with an instant delay in operation and an error in operation in the case of the operation of the robot in an off-road place such as a stricken area. Further, a deviation can occur between the actual pivot angle of each of the crawlers and the rotating angle of the associated knob. Moreover, the operator cannot finely and timely remote-control the robot since data, such as that each of the rollers comes to a stop before fulfilling a pivot-angle instruction due to a pivoting resistance, is not fed back to the knob. That is, the operator cannot remote-control the robot by directly feeling in his body the posture of each of the crawlers, and accordingly, a problem arises in that the robot can experience a downfall or a sidewise turn-over during its operation.
Further, in the case of travel on such an off-road place, the operator has to remote-control the robot while monitoring an inclinometer or the like, always paying the closest attention thereto in order to prevent the robot from falling off a precipice. That is, whether the robot falls down or not is dependent upon the operator's monitoring abilities and manipulation skills, and accordingly, the operator is greatly strained. Further, care should be taken to prevent the operator from falling down, in addition to taking care for the safe operation of the robot. Accordingly, if the operator has to remote control the robot over a long distance in an stricken area in a wide area disaster while he accompanies the robot, he can become greatly exhausted, and accordingly, there is a fear that he may have an accident such as a downfall over a precipice, and further, his monitoring abilities and manipulation skills deteriorate, resulting in a problem of erroneously causing the robot to fall down.